(176) 



olive green, browner in age, and at length a deep brown. Utricles 

 elliptical, somewhat oblong and obtuse, shortly pedicellate, scattered 

 upon the upper branches. 



The habit of this species is so peculiar, and so unlike that of any 

 other species of the genus, and indeed of any other British Alga, that 

 it cannot fail to be recognised at a glance. The stems and branches are 

 of considerable thickness, generally from half a line to one or even two 

 lines in diameter, much branched in an irregidar manner ; these, how- 

 ever, are not the real branches of the plant, but are composed of 

 innumerable excessively fine capillaceo-multifid filaments, twisted, inter- 

 woven, and compacted together, so as to resemble a piece of packthread, 

 or rather a piece of felt, only the apices of the filaments being free, 

 give the frond the appearance, when floating freely in the water, of 

 being covered by a dense mass of capillary filaments, so delicate, that 

 when removed from the water they fall down and become closely 

 appressed to the central portion, giving the whole the appearance of 

 a spongy cord. 



It is difiicidt to account for this peculiarity in the habit of this species. 

 Many of the filamentous Algse have a tendency to be twisted into rope- 

 like bundles, but none of them to anything like such an extent as the 

 present, in which the peculiarity is so remarkable as to become one of 

 structure rather than of habit. 



The species is a common one, and seems partial to the fronds of 

 Fiicus vesiculosus, which are at times, near low-water, almost covered with 

 its shaggy-looking fi'onds. 



EXPLANATION OF PLATE CLXXVIL 



Fig. 1. — Ectocarpus tomentosus, natural size. 

 2. — Branch. 



3. — Same, more magnified. 

 4. — Fruit. All magnified. 



